Expiratory valve

ABSTRACT

The present invention relates to an expiratory valve ( 10 ) of a ventilation device ( 100 ), comprising a valve body ( 12 ) having a fluid inlet ( 14 ) and a fluid outlet ( 16 ) for breathing air of a patient formed therein, said valve body ( 12 ) defining a fluid flow path between fluid inlet ( 14 ) and fluid outlet ( 16 ), with the cross-sectional area of said fluid flow path expanding in the direction towards the fluid outlet ( 16 ).

The present invention relates to an expiratory valve of a ventilationdevice, comprising a valve body having a fluid inlet and a fluid outletfor breathing air of a patient formed therein, the valve body defining afluid flow path between the fluid inlet and the fluid outlet, with thecross-sectional area of the fluid flow path expanding in the directiontowards the fluid outlet.

This expiratory valve is used in a ventilation device for mechanicalventilation of patients. The present invention also relates to such aventilation device.

In mechanical ventilation, breathing air is supplied to a patient inmechanical manner, as a rule under positive pressure. Mechanicalventilation can support or completely replace the patient's ownbreathing. Supply of the ventilation air takes place in successiveventilation cycles. Each ventilation cycle comprises an inspirationphase followed by an expiration phase. The ventilation air is suppliedduring the inspiration phase of a respective ventilation cycle, as arule mechanically or in any case in machine-assisted manner and at apositive pressure with respect to the pressure prevailing in thepatient's airways. Expiration takes place during a subsequent expirationphase of the ventilation cycle. As a rule, there is no positive pressureor negative pressure applied to the airways in the expiration phase.Rather, expiration is to take place passively by relaxing the airwayswith respect to ambient pressure, in which patient's own expiratoryefforts are to be supported as much as possible. Expiration of thebreathing air and discharge of the breathing air to the environment isto be effected with the aid of the expiratory valve described herein.The expiratory valve is arranged in the ventilation system in a conduitfor exhaled air, as a rule at the downstream end of this conduit. On itsside facing away from the patient, there is usually ambient pressureprevailing. When a positive pressure with respect to this pressure isapplied to the valve during an expiration phase from the side of thepatient, the expiratory valve is to open and permit discharge of theexhaled air to the environment. In doing so, the expiratory valve is toreliably recognize the beginning and the end of expiration phases andreact accordingly. To this end, there is used a valve membrane which,depending on whether a sufficiently high positive pressure with respectto its side facing the environment is present on its side facing theairways, opens or closes a fluid passage between the airways and theenvironment.

In the past, there was frequently the problem arising that theexpiration valve caused unpleasantly loud noise during operation. Insome cases, it could even be observed that oscillating pressurefluctuations in the exhaled air were caused or increased by theexpiratory valve, which in the end led to malfunctions in ventilation.In case of this phenomenon known as auto trigger or auto cycle, pressurefluctuations caused by, or increased by, the expiratory valve areerroneously detected by the ventilation device as end of the expirationphase, and the ventilation device prematurely initiates the nextinspiration phase. This is very unpleasant for the mechanicallyventilated patient and may even lead to danger for the mechanicallyventilated patient. The expiratory valve according to the invention isintended to avoid or at least reduce such problems.

In comparison with the expiratory valves used so far, the expiratoryvalve according to the invention, as set out in the initial paragraphsof this disclosure, permits improved guiding of the exhaled air. Inparticular, the expiratory valve is more sensitive in reacting to thebeginning and the end of the expiration phase, and the generation ofnoise during operation of the expiratory valve is clearly suppressed.Moreover, it is possible to better control the phenomenon of autotrigger or auto cycle.

The cross-sectional area of the fluid flow path, which expands in thedirection towards the fluid outlet, is particularly well matched to thevolume flow, which increases towards the fluid outlet, of the fluid (theexhaled air) flowing during expiration through the expiratory valve,which is opened in this phase. The larger the volume flow, the largerthe cross-sectional area available in the fluid flow path. Inparticular, partial volumes of the fluid flow path with respect toangular portions of equal size each change along a circumference of thefluid inlet, such that these partial volumes increase in the directiontowards the fluid outlet. This reduces the formation of turbulence anddisturbances in the fluid flow and provides the possibility that theexpiratory valve can react to changes in the flow of exhaled air in theairways in much more reliable, but at the same time also more sensitivemanner. Retroactive pressure effects, which in conventional expiratoryvalves often led to the aforementioned auto trigger malfunctions, occurfar less.

The cross-sectional area of the fluid flow path is to be understood asbeing the area of the space available for the fluid flow incross-sectional areas transverse to, in particular orthogonal to, themain direction of the fluid flow between fluid inlet and fluid outletwhen the expiratory valve is opened.

The expiratory valve is designed such that breathing air duringexhalation, i.e. during the expiration phase, may enter the expiratoryvalve by way of the now open fluid inlet, in particular may enter avalve plenum enclosed by the expiratory valve. During the inspirationphase, the fluid inlet is preferably closed.

The fluid outlet is designed such that exhaled breathing air can bedischarged to an environment.

In embodiments, the valve body defines a cup-shaped valve plenum which,at least in part is enclosed on its lower side by the valve body, inparticular by a valve bottom formed by the valve body and optionally byan outer edge originating from the valve bottom and constituted by thevalve body as well, and into which the fluid inlet opens. On the topside thereof, the valve plenum may be confined by a valve membraneconstituting a cover. The valve plenum defines a cavity which may havefluid (exhaled breathing air) applied thereto via the fluid inlet andfrom which the fluid (exhaled breathing air) can be discharged via thefluid outlet. In particular, the valve plenum has the fluid flow pathformed therein between fluid inlet and fluid outlet. In particular, thevalve plenum is at least partially confined by a valve bottom on itslower side, and the fluid inlet opens into the valve bottom. The valvebottom may extend in particular in dish-like manner between the fluidinlet and an outer edge of the valve body (in particular, the valveplenum), with the outer edge of the valve bottom at the same timeconstituting the outer edge of the valve body. The term “dish-like” isto point out that the valve bottom, apart from a possible channel-likerecess around the fluid inlet still to be described in more detail,extends in substantially flat or flat conical manner between the fluidinlet and an outer edge. The fluid inlet then is formed in particular ina central part of the valve bottom. The fluid inlet may have inparticular a circular cross-sectional area with an also circular fluidentry surface.

The valve bottom in particular may originate from an edge of the fluidinlet defining a fluid entry surface. There is no step created betweenthe fluid entry surface and the valve bottom. In this manner, there areavoided sharp-edged boundaries of the fluid inlet with respect to thevalve plenum. This enhances the formation of an as quiet as possibleflow of the fluid into the expiratory valve as well as through theexpiratory valve during the expiration phase. In case of knownexpiratory valves, the fluid inlet in contrast projects into the valveplenum, in particular the fluid inlet projects a certain distance beyondthe valve bottom. The valve bottom then does not originate from the edgeof the fluid inlet defining the fluid entry surface, and the fluid flowpasses a step when flowing into the valve plenum, which enhances theformation of turbulence and stalls or air stream separation of the fluidflow flowing into the expiratory valve.

For reducing the generation of noise and retroactive pressure effects,it may also be expedient when the valve plenum has an aerodynamicallyefficient design in terms of flow along the fluid flow path betweenfluid inlet and fluid outlet. The aerodynamically efficient design ofthe valve plenum, in particular, of the fluid flow path, may be enhancedin particular when the valve bottom, starting from an inside of thefluid inlet at the edge of the fluid entry surface, has a roundedcontour on its side facing the valve plenum. The fluid flow entering thevalve plenum from the fluid inlet thus reaches the fluid flow path insubstantially non-swirling manner and without stalls, and flows towardsthe fluid outlet. This results in a reduction of operating noise whenthe fluid outlet is opened. Moreover, retroactive pressure effects intothe breathing air conduit connected to the fluid inlet are effectivelysuppressed, so that the risk of erroneous detections of an end of theexpiration phase by the ventilation device is reduced.

The flow-optimized design of the valve plenum, in particular such thatonly rounded contours are formed along the fluid flow path in the valveplenum from fluid inlet to fluid outlet is considered to constitute asubject matter of the present invention that is independently worthprotecting. The applicant reserves the right to claim independentprotection for this, independently of the configuration of the fluidflow path with a cross-sectional area expanding towards the fluidoutlet.

Certain embodiments may be formed such that the valve bottom bulges inaxial direction in a portion around the fluid inlet. The wording “bulgesin axial direction” is to point out that the valve bottom has a convexconfiguration at least in a section including a fluid inlet axis, namelyin a portion located between the edge of the fluid inlet and the outeredge of the valve bottom. Convex means that, in such sectional view, aline connecting two points on the valve bottom extends through the valveplenum. The valve bottom accordingly forms a groove or channel extendingaround the fluid inlet, with the bottom of said channel bulging in axialdirection between the edge of the fluid inlet and the outer edge of thevalve bottom. With such a design, the cross-sectional area of the fluidflow path between fluid inlet and fluid outlet presents itself in eachcase as the area of the valve plenum in a radial section from the fluidinlet axis to the outer edge of the valve plenum. In contrast to this,the valve bottom of expiratory valves presently in use has a flatconical configuration, i.e. it does not form a bulge or protuberance.

In particular, the design may be such that the axial bulge orprotuberance has a depth that varies around the circumference of thefluid inlet. The depth of the bulge can be defined as a distance,measured in axial direction, between the valve bottom at the edge of thefluid inlet and the valve bottom at the deepest location of the bulgealong a section from the edge of the fluid inlet to the outer edge ofthe valve bottom. In particular, the depth of the bulge is to increasein circumferential direction towards the fluid outlet. Thus, partialvolumes of the bulge, with respect to angular portions of equal sizeeach, change along the circumference of the fluid inlet, such that thesepartial volumes increase in size in the direction towards the fluidoutlet. In certain embodiments, the depth of the bulge incircumferential direction may be smallest on a side opposite the fluidoutlet, and in circumferential direction may be largest on the sidelocated towards the fluid outlet.

As mentioned hereinbefore, the fluid inlet may be arranged in particularin a central portion of the valve plenum. The fluid outlet may bearranged at a further outward location with respect to the fluid inlet,in particular further outside in radial direction, in particular at anouter edge of the valve plenum. With a central arrangement of the fluidinlet, the cross-sectional area of the fluid flow path between the fluidinlet and the fluid outlet presents itself in each case as across-sectional area of the valve plenum in a respective radial sectionfrom the fluid inlet axis to the outer edge of the valve plenum.

The valve body can be made in particular of plastics material. Forexample, it is expedient to produce the valve body in aninjection-molding process. The valve body then is an injection-moldedpart. For example, the valve body together with the valve bottom can bemade from a plastics material suitable for injection-molding, such aspolyethylene, polypropylene or another thermoplastic plastics material.

In certain embodiments, the valve body may have a fluid inlet portionhaving the fluid inlet formed therein. In particular, the fluid inletportion may be formed integrally with the valve body, and thus may beformed as an injection-molded part in the event that the valve body isan injection-molded part. The fluid inlet portion in particular mayextend from the valve bottom, in particular from a lower side of thevalve bottom. The fluid inlet portion may extend e.g. orthogonally withrespect to the valve bottom. The fluid inlet axis designates animaginary line in the longitudinal direction of the fluid inlet portion,which is arranged centrally with respect to the fluid inlet portion.With the fluid entry surface being orthogonal to the fluid inlet, thefluid inlet axis is orthogonal to the fluid entry surface defined by thefluid inlet and is arranged centrally with respect to the fluid entrysurface. In certain embodiments, the fluid inlet portion may define afirst pin-like protrusion which may be designed for connection of abreathing air tube. For example, the first pin-like protrusion may havea cylindrical or conical shape, and in particular may be designed as acylindrical or conical pipe fitting having the fluid inlet formedtherein. The fluid inlet in particular may have a circularcross-sectional area.

In certain embodiments the valve body may have at least one stiffeningor reinforcing rib formed around the fluid inlet. The valve body may beprovided in particular with a plurality of reinforcing ribs formedaround the fluid inlet. The plurality of reinforcing ribs may bearranged in succession, in particular in specific intervals from eachother, around a circumference of the fluid inlet. A single reinforcingrib, for example, may be designed as a solid body surrounding the fluidinlet. The reinforcing rib(s) are formed in particular on a lower sideof the valve bottom and thus on a side of the valve bottom facing awayfrom the fluid flow path, so that they do not interfere with the fluidflow between fluid inlet and fluid outlet.

The reinforcing rib or ribs are suitable to reinforce the valve bottom,in particular in the bulging portion surrounding the fluid inlet. Theprovision of reinforcing rib(s) leads to an increase in the secondmoment of area of the valve body, in particular the valve bottom, acrossthe cross-sectional area of the fluid flow path. The valve body becomesmore torsion-resistant in this region, so that the fluid flow enteringthe valve plenum and flowing along the fluid flow path induces lesservibrations of the valve body, especially the valve bottom. This inhibitsabove all the generation of noise, but there are also caused much lesserretroactive pressure effects that become felt in the breathing airconduit connected to the fluid inlet.

It is advantageous to form the at least one reinforcing rib integrallywith the valve body. The term integral is to be understood to the effectthat the at least one reinforcing rib and the valve body aremanufactured as one component part, for example, that the at least onereinforcing rib is produced in the same injection-molding process as thevalve body, in particular as a single-component injection-molded part.

The at least one reinforcing rib may advantageously extend outwardlywith respect to an edge of the fluid inlet. The expression outwardly isto designate the direction of the at least one reinforcing rib, which isarranged such that it stiffens or reinforces the portion of the valvebottom between the edge of the fluid inlet and the outer edge of thevalve bottom as efficiently as possible. In particular, the at least onereinforcing rib may extend in radial direction with respect to a centerof a cross-sectional area of the fluid inlet. However, it is alsoconceivable that the at least one reinforcing rib does not extendexactly in radial direction, but in addition extends in circumferentialdirection, for example spirally towards the outer edge of the valvebottom. The at least one reinforcing rib in particular may be arrangedoutside of the edge of the fluid inlet.

The at least one reinforcing rib may comprise at least one firstreinforcing rib and at least one second reinforcing rib. The at leastone first reinforcing rib is an inner reinforcing rib that is arrangedradially inside of the second reinforcing ribs. Accordingly, the atleast one second reinforcing rib is an outer reinforcing rib. The atleast one first reinforcing rib in particular extends from the edge ofthe fluid inlet along the valve bottom towards the outside. The at leastone second reinforcing rib extends in particular from an outer edge ofthe valve bottom towards the inside. The at least one first reinforcingrib extends in particular between the edge of the fluid inlet and thebulging portion of the valve bottom. The at least one second reinforcingrib extends in particular between the bulging portion of the valvebottom and an outer edge of the valve bottom. In particular, the atleast one second reinforcing rib terminates in a flange-like shoulderformed at the outer edge of the valve bottom. The shoulder may have, forexample, at least one step extending around the edge of the valvebottom, preferably at least two spaced apart steps, with the at leastone second reinforcing rib merging into the step or an inner one of thesteps, respectively.

Moreover, the valve body in particular may define a fluid outlet portionhaving the fluid outlet formed therein. The fluid outlet portion inparticular may have a second pin-like protrusion. The fluid outletportion in particular may be formed integrally with the valve body, forexample in the form of an injection-molded part as well. The secondpin-like protrusion in particular may have a cylindrical or conicalshape. If desired, the second pin-like protrusion may be formed, forexample, as a cylindrical or conical pipe fitting having the fluidoutlet formed therein. However, the second protrusion often will opendirectly into the environment. The fluid outlet in particular may have acircular cross-sectional area.

The bulging portion of the valve bottom, which defines the fluid flowpath between fluid inlet and fluid outlet, may merge into the fluidoutlet portion. The bulging portion of the valve bottom in particularmay merge into a sidewall of the fluid outlet portion. In particular,the groove or channel defined by the bulging valve bottom has a maximumdepth at the transition to the fluid outlet portion.

As in case of the fluid inlet portion, also the fluid outlet portion inparticular may extend away from the valve bottom, in particular from alower side of the valve bottom. The fluid inlet portion may extendorthogonally with respect to the valve bottom.

Furthermore, it is advantageous when the valve body has a support on thetop side of which a valve membrane can be placed with an abutment areaformed at the outer edge of the same, with the support having an unevendesign on its top side.

As described hereinbefore, the expiratory valve comprises furthermore avalve membrane associated with the fluid inlet, which can be displacedat least between a position closing the fluid inlet and a positionopening the fluid inlet. The valve membrane may be designed without adrive of its own, so that it can be displaced between closing positionand opening position merely by pressure differences between its sidefacing the fluid inlet and its side facing away from the fluid inlet. Inaddition or as an alternative, however, there may also be provided anactuator displacing the valve membrane in reciprocating manner betweenclosing position and opening position. This actuator preferably isdriven by the ventilation device. This valve membrane has its abutmentarea, which is formed at the outer edge of the same, resting on the topside of the support. The expiratory valve in particular comprisesfurthermore a clamping member, for example, a clamping ring, cooperatingwith the valve body in such a manner that the clamping memberestablishes clamping engagement with the valve membrane. By way of thisclamping engagement, which is effected in particular at the outerperiphery of the valve membrane by clamping engagement with the clampingmember, the valve membrane is fixed to the valve body. In this regard,the valve membrane can be fixed to the valve body by the clamping memberin such a manner that, when a positive pressure is present on its sideassociated with the fluid inlet as compared to its side associated withthe valve plenum, the valve membrane can be brought into a positionopening the fluid inlet with respect to the valve plenum. As long asthis is not the case, in particular with equal pressures or a negativepressure on its side associated with the fluid inlet as compared to itsside associated with the valve plenum, the valve membrane remains in aposition closing the fluid inlet with respect to the valve plenum.

The present invention in addition relates to a ventilation devicecomprising an expiratory valve of the type described hereinbefore, whichcan be connected to an expiration air conduit.

The invention will be explained in more detail in the following by wayof an embodiment with reference to the drawings, wherein:

FIG. 1 shows a ventilation device for mechanical ventilation ofpatients, comprising a control unit, a monitor as well as tubes forsupplied breathing air and for exhaled air;

FIG. 2 shows a sectional view of an expiratory valve according to anembodiment;

FIG. 3 shows a perspective view of the valve body of the expiratoryvalve of FIG. 2 from below; and

FIG. 4 shows a perspective view of the valve body of the expiratoryvalve of FIG. 2 from above.

For like or functionally alike components, the same reference numeralswill be used in all of the figures. A detailed description of suchcomponents will be given in each case for the first figure only whichshows the respective reference numeral. It is to be understood that thesame description also applies to all other figures in which thecomponent bearing the same reference numeral is shown, unless pointedout specifically to the contrary.

FIG. 1 shows a ventilation device 100 for mechanical ventilation ofpatients. The ventilation device 100 comprises a rack 102 that ismovable on rollers, along with a control unit 110 and a monitor 120 aswell as a conduit 130 for ventilation air supplied by the device and aconduit 140 for exhaled air. The conduit 130 for supplied ventilationair comprises a first ventilation air tube 132 extending from thecontrol unit 110 to a humidification unit 134 where the ventilation airis passed through a water reservoir. From the humidification unit 134, asecond ventilation air tube 136 extends to a T-piece 138. From theT-piece, the ventilation air provided by the ventilation device 100during an inspiration phase of the ventilation cycle is supplied to thepatient via a conduit 150. Via conduit 150, the air exhaled by thepatient during an expiration phase of the ventilation cycle is alsoreturned to the ventilation device 100. To this end, an additionalbreathing air tube 142, belonging to conduit 140 for exhaled air,branches off from the T-piece 138. The breathing air tube 142 leads toan expiratory valve, generally designated 10, which will be explained inmore detail in the following with reference to FIGS. 2 to 4.

FIG. 2 shows a sectional view of the expiratory valve 10 according to anembodiment, as utilized in FIG. 1. The expiratory valve 10 comprises avalve body 12 having formed therein a fluid inlet 14 and a fluid outlet16 for breathing air exhaled by a patient. FIGS. 3 and 4 showperspective views of this valve body 12, FIG. 3 showing a view frombelow approximately from the direction of the arrow designated 12 inFIG. 4, and FIG. 4 showing a view from above approximately from thedirection of the arrow designated 12 in FIG. 3. FIG. 2 illustrates theexpiratory valve 10 prior to installation in a ventilation device 100 sothat the breathing air tube 142 is not yet connected. In the operativestate, i.e. after installation of the expiratory valve 10 in aventilation device 100 according to FIG. 1, the breathing air tube 142is connected to the fluid inlet 14. Air exhaled by the patient is thuspassed to the expiratory valve 10 via the fluid inlet 14. Upon passagethrough the expiratory valve 10, the exhaled air is sent via the fluidoutlet 16 to a surrounding environment of the ventilation device 100.

The expiratory valve 10 comprises a so-called valve plenum 18. The valveplenum 18 defines a cavity which is adapted to be acted upon by fluid(exhaled breathing air) via the fluid inlet 14 and from which fluid(exhaled breathing air) can be discharged via the fluid outlet. Thus, inthe valve plenum 18 there is thus formed a fluid flow path between thefluid inlet 14 and the fluid outlet 16 by the valve body 12 and a valvemembrane 20. The fluid inlet 14 is designed such that breathing airduring exhalation, i.e. during an expiration phase of the ventilationcycle, can enter the valve plenum 18. During an inspiration phase of theventilation cycle, i.e. when breathing air is supplied to the patientmechanically via the ventilation conduit 130, the fluid inlet 14 is tobe closed. To achieve this, there is provided the valve membrane 20 thatis associated with the fluid inlet 14. The valve membrane 20 can bedisplaced at least between a position closing the fluid inlet 14 and aposition opening the fluid inlet 14. The valve membrane 20 in particularis designed such that a central portion of the valve membrane 20 abutsthe fluid inlet 14 so as to close a fluid entry opening 22 formed at thefluid inlet 14, as long as the pressure on the side of the valvemembrane 20 associated with the fluid inlet 14 is not higher by apredetermined pressure than the pressure prevailing on the side of thevalve membrane 20 facing away from the fluid inlet 14 (which usually isthe ambient pressure). The valve membrane 20 then is in a positionclosing the fluid inlet 14 or the conduit 140 with respect to the valveplenum 18. This is the position taken by the valve membrane 20 duringthe inspiration phases. With a sufficiently high positive pressure onits side associated with the fluid inlet 14 or the conduit 140 forexhaled air as compared to the pressure on its side facing away from thefluid inlet 14 or the conduit 140 for exhaled breathing air, the valvemembrane 20 moves into a position opening the fluid inlet 14 withrespect to the valve plenum 18, so that breathing air from the conduit140 for exhaled breathing air can flow into the valve plenum 18. Thistakes place usually during the expiration phases. The valve membrane 20is made of a plastics material, in particular of a plastics materialhaving elastic properties, for example a silicone or polysiloxaneplastics material. The valve membrane 20 may be installed such that itabuts an edge 26 of the fluid inlet 14 surrounding the fluid entryopening 22 in biased manner and without a positive pressure beingapplied on its side facing the conduit 140 for exhaled breathing air.When a sufficiently large positive pressure is applied to its sidefacing the conduit 140 for exhaled breathing air, the valve membrane 20disengages from the edge 26 of the fluid inlet 14 surrounding the fluidentry opening 22, so that exhaled breathing air can flow into valveplenum 18. However, in addition or as an alternative there may also beprovided an actuator displacing the valve membrane 20 in reciprocatingmanner between closing position and opening position. This actuator isdriven preferably by the ventilation device and engages, for example, inthe central portion of the valve membrane 20 on the side of valvemembrane 20 facing away from the fluid entry opening 22. The respectiveposition of the valve membrane 20 determines the volume of the valveplenum 18 and the fluid flow path formed between valve membrane 20 andvalve body 12.

The valve body 12 comprises a valve bottom 24 extending on a lower sideof the valve plenum 18 from the fluid inlet 14 outwardly so as to reachan outer edge of the valve plenum or the valve bottom. The valve bottom24, together with the valve membrane 20, defines the fluid flow pathformed in valve plenum 18 between fluid inlet 14 and fluid outlet 16. Inparticular, the valve body 12 in certain embodiments forms a cup-shapedvalve plenum 18 which is at least confined in part on its lower side bythe valve bottom 24 and into which the fluid inlet 14 opens. The valvebottom 24 in particular can extend in dish-like manner between the fluidinlet 14 and an outer edge of the valve body 12 (in particular of thevalve plenum 18), with the outer edge of the valve bottom 24constituting at the same time the outer edge of the valve body 12. Thefluid inlet 14 then is formed in particular in a central part of valvebottom 24. The fluid inlet 14 may have in particular a circularcross-sectional area and have an also circular fluid entry surface 22.An edge 26 of the fluid inlet 14 defining the fluid entry surface 22thus forms an inner edge of the valve bottom 24 which extends startingfrom the edge 26 on the lower side of the valve plenum 18 to an outeredge of the valve body 12. The outer edge of the valve body 12 in radialdirection is located farthest away from the fluid inlet 14. Thus, edge26 does not protrude from the valve bottom 24—at least not abruptly orwith a sharp edge—, but rather, the valve bottom 24 begins directly atthe edge 26 of the fluid entry opening 22 and extends in a smoothlycurved contour from this edge 26 outwardly. Due to this configuration,sharp edges are avoided which, when air flows around the same, couldcause air stream separation and the generation of noise associatedtherewith.

The valve bottom 24 has a dish-like configuration. This is to expressthat the valve bottom 24 extends with a substantially flat, or at themost flat conical, configuration between the inner edge 26 and the outeredge of the same. Possible recesses in the valve bottom 24, for examplea groove or channel still to be described in more detail hereinafter,are formed such that an in total rounded and flow-matching contour iscreated, having various, smoothly merging curvatures.

While the fluid inlet 14 is arranged in a central portion of the valveplenum 18, the fluid outlet 16 is located radially further outside withrespect to the fluid inlet 14. In particular, the fluid outlet 16 isarranged at an outer edge of the valve plenum 18. At the location of thevalve outlet 16, the valve body 12 is provided, in particular in anouter wall of the valve bottom 24, with an exit opening through whichbreathing air can flow from the valve plenum 18 to the fluid outlet 16.The exit opening also is provided with edges that are smoothly curvedand thus have a configuration that is expedient in terms of flow, sothat a flow of breathing air along sharp edges upon discharge from thevalve plenum 18 is avoided.

The valve body 12 is made from a plastics material, for examplepolyethylene, polypropylene or another thermoplastic plastics material.The valve body 12 is an injection-molded part, i.e. it is produced in aninjection-molding method. In particular, the valve body 12 may bedesigned such that it can be manufactured in a single injection-moldingprocess, in particular in the form of a single-componentinjection-molded part.

The valve body 12 has a fluid inlet portion 28 in which the fluid inlet14 is formed. The fluid inlet portion 28 in particular is formedintegrally with the valve body 12. The fluid inlet portion 28 extendsaway from the valve bottom 24, in a direction from the lower side of thevalve bottom 24 substantially along an axial direction A of the fluidinlet 14. In addition, the fluid inlet portion 28 extends transverselyto the valve bottom 24, i.e. it protrudes from a lower side of the valvebottom 24 in the axial direction A of the fluid inlet 14. The axialdirection A designates a fluid inlet axis, i.e. an imaginary line in thelongitudinal direction of the fluid inlet portion 28 which is locatedcentrally with respect to the fluid inlet 14. With the fluid entrysurface 22 being arranged orthogonally with respect to the fluid inlet14, the fluid inlet axis A extends orthogonally with respect to thefluid entry surface 22 defined by the fluid inlet 14, and is locatedcentrally with respect to the fluid entry surface 22.

The fluid inlet portion 28 forms a first pin-like protrusion that isconfigured in particular for connecting a breathing air tube, forexample the breathing air tube 142 illustrated in FIG. 1. In the variantillustrated in FIG. 2, the first pin-like protrusion has an inparticular cylindrical shape. In other modifications, the pin-likeprotrusion could also be formed so as to slightly taper towards the freeend of the same, for example with a slightly conical taper. The firstpin-like protrusion may be formed in particular as a pipe fitting havingthe fluid inlet 14 formed therein.

The valve body 12 moreover defines a fluid outlet portion 30 having thefluid outlet 16 formed therein. The fluid outlet portion 30 inparticular may form a second pin-like protrusion which may have acylindrical or tapering (in particular conical) shape. The secondpin-like protrusion may be formed for example as a cylindrical pipefitting having the fluid outlet 16 formed therein. Also the fluid outletportion 30 may be formed in particular integrally with the valve body12. The fluid outlet 16 in particular may have a circularcross-sectional area. The fluid outlet 16 need not necessarily beconnected to a further conduit, but may open directly into thesurroundings, so that exhaled air is discharged via the fluid outlet 16to the surrounding environment. The fluid outlet portion 30, on itsradially inner side, is connected to the valve plenum 18 via theafore-mentioned exit opening, so that fluid that has flown into theexpiratory valve 10 is passed via the exit opening to the fluid outletportion 30.

Similar to the fluid inlet portion 28, the fluid outlet portion 30 canalso extend in particular from the valve bottom 24, in particular from alower side of the valve bottom 24. The fluid outlet portion 30 mayextend orthogonally with respect to the valve bottom 24 and/or in adirection parallel to the fluid inlet portion 28, as can easily be seenin FIGS. 2 to 4.

The fluid flow path in the valve plenum 18 has a cross-sectional areawhich, as measured transversely to the fluid flow between fluid inlet 14and fluid outlet 16, is expanding from the fluid inlet 14 towards thefluid outlet 16. This is achieved by a specific configuration andarrangement of the valve body 12, in particular the valve bottom 24 andthe valve membrane 20. The valve bottom 24 primarily constitutes aboundary of the fluid flow path on the bottom side. The valve membrane20 primarily constitutes a boundary of the fluid flow path on the topside of the same. While it is very well possible to make use of a valvemembrane 20 similar to conventional valve membranes, the valve bottom 24is designed such that the cross-sectional area of the fluid flow pathincreases towards the valve outlet 16. In particular, the valve bottom24 is designed such that the distance of the same from the valvemembrane 20 increases from the fluid inlet 14 towards the fluid outlet16. This can take place in one or more stages, but in particular takesplace continuously from the fluid inlet 14 towards the fluid outlet 16.With the geometry of the expiratory valve 10 illustrated in FIGS. 2 to4, having the fluid inlet 14 arranged radially inside and centrally andhaving the fluid outlet 16 arranged radially outside, it is expedientfor example to design the fluid flow path such that partial volumes ofthe fluid flow path with respect to angular portions of equal size eacharound the fluid inlet 14 change along the circumference of the fluidinlet 14 such that these partial volumes increase in size in thedirection towards the fluid outlet 16. Such an effect can be achieved,for example, when a plane along which the valve bottom 24 extends isinclined with respect to a plane along which the valve membrane 20extends, such that these two planes extend away from each other towardsthe fluid inlet 16. While for example, the valve membrane 20 will as arule extend in a plane orthogonal to the fluid inlet axis A (in FIGS. 2and 3 this plane is illustrated very schematically by broken linesdesignated C), there may be specific embodiments in which the valvebottom 24 can extend along a plane that is inclined with respect to thefluid inlet axis A at an angle differing from 90 degrees. The planealong which the valve bottom 24 extends is to designate the planefollowing the central extension of the valve bottom 24, with possibleindividual (e.g. dent-like) bumps and recesses, respectively, of thevalve bottom 24 being disregarded. However, the valve bottom 24 has acontinuous recess determining the cross-sectional area of the flow pathbetween the fluid inlet 14 and the fluid outlet 16, as will still bedescribed in the following, so that the plane along which the valvebottom 24 extends, in general, will be determined by the course of thisrecess (i.e. the course of the deepest locations in the successivecross-sections following the fluid flow path). In FIGS. 2 and 3, thelocation of this plane is illustrated very schematically by line B. Itcan be seen that this plane is not parallel to the plane along whichvalve membrane 20 extends (the latter plane extends orthogonal to thefluid inlet axis A), but rather forms an angle to the fluid inlet axis Athat is different from 90 degrees. This implies that the normal vector Nof this plane is not parallel to the fluid inlet axis A, but ratherforms an angle α with respect to the same. Normally, the normal vector Nwill be inclined with respect to the fluid inlet axis A towards thefluid outlet 16, as it is also indicated in FIGS. 2 and 3.

The increase in the cross-sectional area of the fluid flow path towardsthe fluid outlet 16 takes account of the fact that the volume flow ofbreathing air flowing towards the outlet increases with decreasingdistance of the fluid flow path from the fluid outlet. The volumeavailable for the volume flow in the valve plenum 18 thus is matched tothe volume flow. Due to such matching of the volume available for thefluid flow, there are avoided stalling effects with resulting swirlingof the breathing air to be exhaled.

Moreover, it can readily be seen from FIGS. 2 to 4 that the valve bottom24 bulges outwardly in axial direction in a portion around the fluidinlet 14. The expression “bulges outwardly in axial direction” is to beunderstood to the effect that the valve bottom 24 has a convex shape atleast in a section containing the fluid inlet axis A, namely in aportion between the edge of the fluid inlet 14 and the outer edge of thevalve bottom 24. In the embodiments illustrated, this may also be asection in radial direction. In FIG. 2, this convex shape is illustratedfor the section through the deepest location of the thus formed bulge 32at the fluid outlet 16 on the left side in FIG. 2 and is illustrated forthe section through the location of the least depth of the bulge 32 onthe right side in FIG. 2. Convex means that, in such a sectional view, aline interconnecting two points on the valve bottom 24 extends throughthe valve plenum 18. Accordingly, the valve bottom 24, in the region ofthe bulge 32 thus created, forms a groove or channel extending aroundthe fluid inlet 14 and having a floor bulging in axial direction betweenthe edge of the fluid inlet 14 and the outer edge of the valve bottom24. The channel thus defines the fluid flow path around the fluid inlet14. The respective deepest point of this channel along the fluid flowpath (in other words: the connection of the deepest points in respectivesections between fluid inlet 14 and the outer edge of the valve bottom24) thus forms a line extending around the fluid inlet 14 and designated34 in FIG. 3. With the radially symmetric geometry of the valve bottom24 having the fluid inlet 14 in the center, as illustrated in thefigures, this line 34 has an elliptical shape due to the differing depthof the channel which still is to be outlined in more detail (theprojection of this line 34 onto a plane, such as the plane C, orthogonalto the fluid inlet axis A has a circular shape). As can readily be seenin FIGS. 2 to 4, the bulging portion of the valve bottom 24 (or thechannel thus formed) defines two fluid flow paths extendingsubstantially around half of the circumference of the fluid inlet 14,which finally open into the fluid outlet 16 on a lateral side (in FIG. 2on the left of the fluid inlet 14). In this respect, the bulging portionof the valve bottom 24 has its outer sidewall merging into the fluidoutlet portion 30. As was already mentioned, all edges along this fluidflow path are provided with a rounded contour counteracting stalls orair stream separation and/or swirling of the fluid flow.

The figures readily show that the axial bulge 32 of the valve bottom 24is of varying depth around the circumference of the fluid inlet 14. Thedepth is to be measured as a distance measured in the direction of thefluid inlet axis A between the valve bottom 24 at the edge 26 of thefluid inlet 14 and the valve bottom 24 at the deepest location of thebulge 32 in a section interconnecting the fluid inlet 14 to the outeredge of the valve bottom 24 (in case of a radially symmetric geometry ofthe valve bottom 24 as shown in the figures, this is a radial sectionthrough valve bottom 24). FIGS. 2 and 3 each illustrate the maximumdepth Tmax at the location of the fluid outlet 16 and the respectiveminimum depth Tmin on the side opposite the fluid outlet 16.

Thus, partial volumes of the fluid flow path with respect to respectiveangular portions of equal size in each case change along thecircumference of the fluid inlet 14, such that these partial volumesincrease with decreasing distance from the fluid outlet 16. It has shownthat this measure contributes quite considerably in reducing flow-causednoise when discharging breathing air during expiration phases as thevolume available is matched to the volume flow of the flowing fluid.

The figures also clearly show that the valve bottom 24 has a roundedcontour starting from an inside of the fluid inlet 14 at the edge of thefluid entry surface 22 on the side thereof facing the valve plenum 18.This is revealed particularly clearly in FIG. 4. Upon passage of thefluid entry surface 22, the fluid flow flows along the rounded inneredges of the channel formed by the bulge 32 to the deepest location ofthe same in order to then flow along the fluid flow path formed by thechannel—following approx. line 34—around the fluid inlet 14 towards thefluid outlet 16. In doing so, the fluid flow passes no sharp edgeswhatsoever that could cause stalls or swirling along with noisegenerated thereby.

The valve body 12 furthermore shows reinforcing ribs 36, 38 formedaround the fluid inlet 14. In FIGS. 2 and 3 some of these reinforcingribs are shown in exemplary manner at numerals 36 and 38. Thereinforcing ribs 36, 38 reinforce the valve bottom 24, in particular theshell formed by the valve bottom 24 in the bulging portion 32. Torsionsof the valve body 22 are effectively suppressed by this additionalreinforcement. The reinforcing ribs 36, 38 thus also contribute inreducing the generation of noise as they suppress vibrations of thevalve body 24 under the influence of a fluid flow in the valve plenum18. However, it is also possible to efficiently suppress undesireddisturbing vibrations of the valve membrane 20. This reduces the riskfor oscillations of the air column in the tube system, which may resultin erroneously triggered control operations (in particular so-calledauto triggers). The reinforcing ribs 36, 38 are formed integrally withthe valve body 12. In this respect, integral is to be understood to theeffect that the reinforcing ribs 36, 38 and the valve body 12 aremanufactured as one single component part. In the embodimentillustrated, the reinforcing ribs 36, 38 are manufactured in the sameinjection-molding process as the valve body 12.

The reinforcing ribs 36, 38 are arranged outside of the fluid inlet 14.As can be seen in the figures, they extend outwardly with respect to theedge 26 of the fluid inlet 10, towards the edge of the valve body 12. Inthe embodiment illustrated, the reinforcing ribs extend in radialdirection with respect to the fluid inlet axis A. However, they may alsoextend from the inside outwardly in rather spiral fashion. In doing so,the reinforcing ribs connect the edge 26 of the fluid inlet 16 to theouter edge of the valve body 12. The reinforcing ribs 36, 38 are formedon a lower side of the valve bottom 24. Thus, they do not interfere withthe fluid flow path formed on the inside of the valve body 12, i.e. onthe top side of the valve bottom 24. As can be seen in the figures, thereinforcing ribs comprise first reinforcing ribs 36 and secondreinforcing ribs 38. The first reinforcing ribs 36 are inner reinforcingribs formed between the edge 26 of the fluid inlet 14 and the bulgingportion 32 of the valve bottom 24. In the embodiment illustrated, thefirst reinforcing ribs 36 connect the edge 26 of the fluid inlet 14 tothe bulging portion 32 of the valve bottom 24. The second reinforcingribs 38 are outer reinforcing ribs extending between the bulging portionof the valve bottom 32 and the outer edge of the valve bottom 24. In theembodiment illustrated, the second reinforcing ribs 38 connect thebulging portion 32 of the valve bottom 24 to the outer edge of the valvebottom 24. The second reinforcing ribs 38 terminate in a flange-likeshoulder 40 formed at the outer edge of the valve bottom 24. Theshoulder 40 may comprise for example at least one step extending aroundthe outer periphery of the valve bottom 24, in particular at least twospaced apart steps, with the second reinforcing ribs 38 merging into thestep or an inner one of the steps, respectively. The step or steps mayform, for example, a ring-like flange extending around the outer edge ofthe valve bottom 24 and giving the stability to the same.

As illustrated in FIG. 2, the expiratory valve 10 comprises furthermorethe valve membrane 20 associated with the fluid inlet 40. In the statemounted in the expiratory valve 10, the valve membrane 20 has anabutment area thereof, which is formed on the outer edge, resting on thetop side of a support 42 which is formed on the top side of the valvebody 12. The support 42 forms a projection extending around the outeredge of the valve body 12 and projecting from the outer edge of thevalve body 12 inwardly, towards the side of the valve plenum 18. Thesupport 42 is also formed integrally with the valve body 12, forexample, in the form of an injection-molded part that is formed in thesame injection-molding process as the valve body 12. During assembly ofthe expiratory valve 10, the valve membrane 20 has its outer abutmentarea brought into abutting contact with the top side of the support 42of the valve body 12, so that the valve membrane 20 rests on the edge 26of the fluid inlet 14 with an abutment area formed in the central partof the same and rests on the support 42 with its abutment area formed inthe outer part of the same. The valve membrane 20 thus defines a topside of the fluid flow path formed in the valve plenum 18. The valvemembrane 20 then is clamped with respect to the valve body 12 by meansof a clamping ring 44 illustrated in FIG. 2. To this end, the clampingring 44 is placed onto the valve membrane and then is rotated withrespect to the valve body 12 in bajonet-like manner. By way of theclamping forces thus created, the valve membrane 20 is deformed to acertain extent at the periphery of the same.

For this reason, the support 42 has an uneven shape on its top side. Thebumps thus formed in the surface of the support 42, which areillustrated in FIG. 4 at numeral 46, compensate the deformation of thevalve membrane 20 that is caused when the clamping ring 44 is clampedwith respect to the valve body 12, so that the formation of folds orwarps at the periphery of the valve membrane 20 in the clamped state canbe suppressed. In particular, there are formed bumps 46 on the top sideof the support 42 in the form of protuberances or bulges or ribs spacedapart from each other along the circumference. These bulges or ribs mayextend radially. It is even better when the bulges or ribs have athread-like design, i.e. a certain pitch with respect to the plane ofthe abutting valve membrane 20 and/or do not only extend in radialdirection, but also in circumferential direction, e.g. extend in spiralmanner around the periphery of the valve body 12. For restricting theclamping forces thus created, it may also be expedient to keep the pitchof the threads formed by the bulges or ribs low and/or to restrict therising portion, e.g. by a stop at the end of a bulge or rib and/or by atransition into a portion at the end of the bulge or rib extendingparallel to the plane of the valve membrane 20. The bumps, in particularin the form of bulges and/or ribs, may be formed integrally with thesupport 42.

The support 42 may be formed so as to extend continuously around theperiphery of the outer edge of the valve body (as shown e.g. by regiondesignated 42 in FIG. 4), or may be formed with interruptions so thatindividual supporting portions are formed arranged in succession alongthe circumference of the outer edge of the valve body 12. In theembodiment according to FIG. 4, such an individual supporting portion 42a is formed on the side of the fluid inlet 16 above the dischargeopening between the valve plenum 18 and the fluid outlet 16.

The top side 46 of the support 42 is formed in uneven manner so that thetop side 46 of the support 42 is arranged in an imaginary curvedsurface, i.e. so that there is no imaginary plane which completelycomprises the top side 46 of the support 42. The imaginary curvedsurface covers a top side of the valve body 12. In particular, it isarranged orthogonally with respect to the fluid inlet axis Aconstituting at the same time a longitudinal axis of the valve body 12.Due to the uneven shape of the top side 46 of the support 42, a planarsurface—when making attempts to place the same on the top side 46 of thesupport—would not contact the entire top side 46 of the support 42.Rather, there would only be individual locations of the planar surfacethat establish contact with the top side 46 of the support 42. Thus, atleast in the state of the expiratory valve 10 in which the same is notinstalled in a ventilation device 100, the planar valve membrane 20 doesnot abut with the entirety of its periphery on the top side 46 of thesupport 42. Rather, there are individual contact locations between valvemembrane 20 and support along the periphery of the valve membrane 20.The unevenness of the top side of the support 42 is such that, only whenthe expiratory valve 10 is installed in the ventilation device 100 andthe valve body 12 is subject to stress causing deformation of the same,the top side 46 of the support 42 comes to lie in a planar surface andthe valve membrane 29 now has its abutment area in sheet-like orfull-area contact with the top side 46 of the support 42.

The valve body 12 comprises at least one mounting lug 50 which isdesigned for engagement with a bayonet-like expiratory valve connectionof a ventilation device 100. The ventilation device then comprises amating engagement member with which the mounting lug 50 engages uponinstallation of the expiratory valve 10 so as to retain the expiratoryvalve 10 to the ventilation device 100. Such a bayonet-type coupling hasthe property that, upon locking of the expiratory valve 10 to theventilation device 100, there are created clamping forces slightlydeforming the valve body 12.

The valve body 12 comprises at least two mounting lugs 50 associatedwith each other. The mounting lugs 50 are arranged at the radially outerperiphery of the valve body 12 around the circumference of the valvebody 12 and project in radial direction from the respective radiallyouter edge of the valve body 12 in order to form respective engagementsurfaces 52 with a corresponding mating engagement member on theventilation device 100. When the mounting lugs 50 are engaged with theirrespective mating engagement members provided on the ventilation device100, the valve body 12, on the respective sides thereof provided withthe mounting lugs 50, will be moved towards the ventilation device 100.In the course of this forced movement, there is stress created in thevalve body 12, and the upper edge 48 of the valve body 12 bends towardsthe ventilation device 100 on the sides thereof on which the mountinglugs 50 are disposed. The uneven design of the top side 46 of thesupport 42 provided on the valve body 12 for the valve membrane 20 isintended to compensate this bending of the valve body 12. When themounting lugs 50 are brought into engagement with the respective matingengagement member on the ventilation device 100, the top side 46 of thesupport 42 is to be flat, i.e. is to be arranged in a plane. The twomounting lugs 50 are arranged opposite each other at an angle of 180°,i.e. are arranged on opposite sides of the valve body 12 across thevalve plenum 18.

The top side 46 of the support 42 is located in an outwardly curvedimaginary surface with respect to the valve plenum 18, which covers thetop side of the valve body 12. In particular, the outwardly curvedimaginary surface, with respect to the valve plenum 18, is locatedfurther outside than an imaginary plane through at least two differentpoints on the top side 46 of the support 42 on sides where the mountinglugs 50 are present (i.e. on the left and right sides in FIG. 4). Thetop side 46 of the support 42 is located in a convexly curved imaginarysurface so that a line connecting two points in the imaginary surfaceextends through the valve plenum 18. The top side 46 of the support 42bulges outwardly starting from the two mounting lugs 50. At thelocations where the mounting lugs 50 are provided, the top side 46 ofthe support 42 does not at all bulge outwardly, whereas it has itsmaximum outward bulge in the middle between the two mounting lugs 50 (inFIG. 4 along a line in vertical direction orthogonally to a connectionbetween the two mounting lugs 50). This takes account of the fact thatthe deformation of the valve body 12, upon mounting of the expiratoryvalve 10 to the ventilation device 100, is strongest at the locationswhere the mounting lugs 50 are provided. At this location, the upperedge 48 of the valve body 12 is bent upwardly most strongly.

In the embodiment illustrated, the curved imaginary surface is a lateralsurface of a cylinder, with the axis of the cylinder being orthogonal toa connecting line between the two associated mounting lugs 50.

Due to the stress applied during mounting of the expiratory valve 10 tothe valve body 12 at the locations where the mounting lugs 50 arepresent, the upper edge 48 of the valve body 12 also bends in the samemanner at these location towards a counter side on the ventilationdevice 100. For compensation of this effect, it is expedient to formalso the valve body 12, or more strictly speaking the upper edge 48 ofthe valve body 12, in corresponding manner to the support 42 for thevalve membrane 20. The upper edge 48 of the valve body 12, upon mountingof the expiratory valve 10 to the ventilation device 100, is to abut ona counter surface of the ventilation device 100 across an as large areaas possible in order to ensure an as tight as possible abutment of thevalve membrane 20. To this end, the valve body 12 has an upper edge 48which is arranged in an outwardly curved imaginary surface with respectto the valve plenum 18. The considerations given hereinbefore for thetop side 46 of the support 42 apply analogously to the design of theupper edge 48 of the valve body 12. In particular, the upper edge 48 ofthe valve body 12 is arranged in a convexly curved imaginary surfacewith respect to valve plenum 18 and bulges outwardly from the at leastone mounting lug 50. The bulge of the upper edge 48 of the valve body 12is larger in a region located between the two mounting lugs 50 than in aregion adjacent one of the two mounting lugs 50.

The uneven shape of the top side 46 of the support 42 and the unevenshape of the upper edge 48 of the valve body 12 are matched with respectto each other. This makes sense as the effect to be achieved for both ofthe same is that, upon mounting of the expiratory valve 10 to theventilation device 100, both the top side 46 of the support 42 and theupper edge 48 of the valve body 12 are arranged in a planar surface. Inparticular, the top side 46 of the support 42 as well as the upper edge48 of the valve body 12 are bulging outwardly in mutually alignedmanner, with the locations of minimum bulge and maximum bulge beingmatched to each other, and in particular are arranged at the samelocation with respect to a plane covering the valve plenum 18. Thedesign is even such that the top side 46 of the support 42 and the upperedge 48 of the valve body 12 have approx. the same bulge and inparticular are arranged in mutually parallel imaginary surfaces.

Each of the mounting lugs 50 has an engagement surface 52 for engagementwith a mating engagement member provided on the ventilation device 100,with the engagement surface 52 being provided with a lead-in chamfer 52that is matched with respect to the bulge of the top side of the support42. As is usual with a bayonet-type engagement, the engagement surface52 as a rule will be formed substantially parallel to an upper edge ofthe mounting lug. In the front portion thereof, there is provided thelead-in chamfer 52 a. In the region of the lead-in chamfer 52 a, theengagement surface 52 then extends at an angle, in particular an acuteangle, with respect to the upper edge of the mounting lug 50. The angleis selected such that a thickness between engagement surface 52 andupper edge of the mounting lug 50 increases with increasing distancefrom the beginning of the engagement surface 52 a. This permits acertain extent of stress to be created upon engaging the mounting lug 50with the mating engagement member on ventilation device 100, whichpromotes a certain force-fit or frictional engagement and thus a firmand safe seating arrangement of the expiratory valve 10 on theventilation device 100. The lead-in chamfer 52 a is designed such that abias is created when the mounting lug 50 is clamped to the ventilationdevice 100, with said bias acting on the upper edge 48 of the valve bodyon the side of the mounting lug 50. This is accompanied by a certaindeformation of the valve body 12 on the side facing the mounting lug 50with respect to sides or locations remoter from the mounting lug 50. Inparticular, the upper edge 48 of the valve body 12, by movement of themating engagement member along the lead-in chamfer 52 a, is broughtcloser to the ventilation device 100. On the other hand, locationsremoter from the mounting lug 50 already abut a contact area of theventilation device 100 and cannot get closer. As a result, there iscreated a deformation of the upper edge 48 of the valve body 12, withthe deformation becoming increasingly stronger towards the mounting lug50. This effects a bias in the valve body 12 which increases withincreasing movement of the mating engagement member along the lead-inchamfer 52 a. The lead-in chamfer 52 a is selected such that, uponclamping, a bias is generated that is just sufficiently large to makethe upper edge 48 of the valve body 12 planar in the clamped state, i.e.that the upper edge 48 of the valve body 12 in the clamped state islocated in a plane covering the valve plenum 18. The upper edge 48 ofthe valve body 12 then is in sheet-like contact with a counter surfaceof the ventilation device 100. The support 42 for the valve membrane 20,which is formed integrally with the valve body 12, is equally bent. Forpermitting the top side 46 of this support 42 to be planar as well inthe state of the expiratory valve 10 mounted to the ventilation device100, it is expedient when the top side 46 of the support 42 is uneven tothe same extent as the upper edge 48 of valve body 12. Accordingly, thelead-in chamfer 52 a of the mounting lug 50 is matched to the bulge ofthe support 42.

For being able to define the end of the lead-in chamfer 52 a as well aspossible and to thus allow the bias for the valve body 12 to be adjustedas accurately as possible, it may be provided that the engagementsurface 52 has a non-tapering portion 52 b following the lead-in chamfer52 a. In the non-tapering portion 52 b, the engagement surface 52 isparallel to the upper edge of the mounting lug 50. A bias and bending ofthe valve body 12 once reached thus does not change any more when thecounter engagement member reaches the non-tapering portion 52 b. Thebias and bending can thus be adjusted in well reproducible manner, as itis no longer of great relevance which location of the non-taperingportion 52 b is reached by the mounting lug 50. Moreover, the engagementsurface 52 is provided with a stop 54 at the end thereof, which definesan end of the engagement movement between mounting lugs 50 andventilation device 100.

The expiratory valve 10 described can be designed as a single-usecomponent, i.e. in the form that it can be used only once and has to bedisposed of after use. Such expiratory valves are inexpensive inmanufacture and nevertheless fulfill the required hygiene standards. Asan alternative the expiratory valve 10 may also be designed to permitmultiple use. To this end, the design of the expiratory valve 10 wouldhave to be such that it can be disinfected after use, for example byautoclaving. The expiratory valve then needs to be designed to withstandautoclaving.

1. An expiratory valve (10) of a ventilation device (100), comprising avalve body (12) having a fluid inlet (14) and a fluid outlet (16) forbreathing air of a patient formed therein, said valve body (12) defininga fluid flow path between the fluid inlet (14) and the fluid outlet(16), with the cross-sectional area of said fluid flow path expanding inthe direction towards the fluid outlet (16).
 2. The expiratory valve(10) of claim 1, wherein the valve body (12) forms a cup-shaped valveplenum (18) which is at least partially surrounded by a valve bottom(24) and into which the fluid inlet (14) opens.
 3. The expiratory valve(10) of claim 1, wherein the valve bottom (24) extends in dish-likemanner between the fluid inlet (14) and an outer edge of the valve body(12).
 4. The expiratory valve (10) of claim 1, wherein the valve bottom(24) originates from an edge (26) of the fluid inlet (14) defining afluid entry surface (22).
 5. The expiratory valve (10) of claim 4,wherein the valve bottom (24), starting from an inside of the fluidinlet (14) at the edge (26) of the fluid entry surface (22), has arounded contour on its side facing the valve plenum (18).
 6. Theexpiratory valve (10) of claim 1, wherein the valve bottom (24) bulgesin axial direction in a portion around the fluid inlet (14).
 7. Theexpiratory valve (10) of claim 6, comprising an axial bulge (32) havinga varying depth around the circumference of the fluid inlet (14).
 8. Theexpiratory valve (10) of claim 7, wherein the depth of the bulge (32)increases in circumferential direction towards the fluid outlet (16). 9.The expiratory valve (10) of claim 7, wherein the depth of the bulge(32) in circumferential direction is smallest on a side opposite thefluid outlet (16).
 10. The expiratory valve (10) of claim 7, wherein thedepth of the bulge (32) in circumferential direction is largest on theside towards the fluid outlet (16).
 11. The expiratory valve (10) ofclaim 2, wherein the fluid inlet (14) is disposed in a central portionof the valve plenum (18).
 12. The expiratory valve (10) of claim 1,wherein the fluid outlet (16) is disposed further outside with respectto the fluid inlet (14).
 13. The expiratory valve (10) of claim 1,wherein the valve body (12) is made of plastics material.
 14. Theexpiratory valve (10) of claim 13, wherein the valve body (12) is aninjection-molded part.
 15. The expiratory valve (10) of claim 1, whereinthe valve body (12) has a fluid inlet portion (28) having the fluidinlet (14) formed therein.
 16. The expiratory valve (10) of claim 15,wherein the fluid inlet portion (28) forms a first pin-like protrusion.17. The expiratory valve (10) of claim 1, wherein the valve body (12)has at least one reinforcing rib (36, 38) formed around the fluid inlet(14), in particular a plurality of reinforcing ribs (36, 38) formedaround the fluid inlet (14).
 18. The expiratory valve (10) of claim 17,wherein the at least one reinforcing rib (36, 38) is formed integrallywith said valve body (12).
 19. The expiratory valve (10) of claim 18,wherein the at least one reinforcing rib (36, 38), with respect to theedge (26) of the fluid inlet (14), extends in outward direction.
 20. Theexpiratory valve (10) of claim 17, wherein the at least one reinforcingrib comprises at least one first reinforcing rib (36) extending from theedge (26) of the fluid inlet (14) along the valve bottom (24).
 21. Theexpiratory valve (10) of claim 17, wherein the at least one reinforcingrib comprises at least one second reinforcing rib (38) extendinginwardly from the outer edge of the valve bottom (24) along the valvebottom (24).
 22. The expiratory valve (10) of claim 1, wherein the valvebody (12) defines a fluid outlet portion (30) having the fluid inlet(16) formed therein.
 23. The expiratory valve (10) of claim 22, whereinthe bulging portion (32) of the valve bottom (24) merges into the fluidoutlet portion (16).
 24. The expiratory valve of claim 1, furthercomprising a valve membrane associated with the fluid inlet, which isdisplaceable at least between a position closing the fluid inlet and aposition opening the fluid inlet.
 25. The expiratory valve (10) of claim1, wherein the valve body (12) further comprises a support (42) onto thetop side of which the valve membrane (20) can be placed with an abutmentarea formed at the outer edge thereof, wherein the support (42) has anuneven design on its top side.
 26. A ventilation device (100),comprising an expiratory valve (10) according to claim 1 that is adaptedto be connected to an expiration air conduit (140).